Wireless transmission device and wireless transmission method

ABSTRACT

A wireless transmission device of the present invention includes n (where n is an integer of two or more) transmission antennas and a delay imparting section for delaying transmission signals supplied to the n transmission antennas by a maximum delay time (n−1)T or less based on a delay time T dependent upon a communication signal, which indicates whether to transmit the transmission signals by way of frequency diversity or multiuser diversity.

This application is a Divisional application Ser. No. 12/065,051, filedon Feb. 27, 2008, and claims priority under 35 U.S.C. §119(a) to PatentApplication No. 2005-253194 filed in Japan on Sep. 1, 2005 and PatentApplication No. 2005-367860 filed in Japan on Dec. 21, 2005, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

TECHNICAL FIELD

The present invention relates to wireless transmission devices andwireless transmission methods and in particular to wireless transmissiondevices and wireless transmission methods for transmitting signals towireless reception devices by use of plural transmission antennas.

The present application claims priorities on Japanese Patent ApplicationNo. 2005-253194 filed in Japan on Sep. 1, 2005 and Japanese PatentApplication No. 2005-367860 filed in Japan on Dec. 21, 2005, thecontents of which are incorporated herein by reference.

BACKGROUND ART

Recently, there are provided methods, mainly adapted to multicarriertransmission systems, in which a plurality of blocks are divided alongfrequency and time axes and which perform scheduling on signalstransmitted to users from wireless transmission devices in units ofblocks. Herein, regions that are secured for users to performcommunications and that are defined along the frequency and time axesare referred to as assignment slots, and blocks serving as the basis fordetermining assignment slots are referred to as chunks.

In the above, there are provided methods that, in order to transmitbroadcast signals, multicast signals, and control signals, blocks whoseranges are broadened in the frequency axis direction are assigned so asto produce frequency diversity effects, thus reducing errorsirrespective of low reception power. In addition, there are providedmethods that, in order to transmit unicast signals in one-to-onecommunications between wireless transmission devices and wirelessreception devices, blocks whose ranges are reduced in the frequency axisdirection are assigned so as to produce multiuser diversity effects,thus improving reception power in wireless reception devices.

FIGS. 16A and 16B show the relationships regarding signals transmittedfrom a wireless transmission device to a wireless reception device withrespect to time (horizontal axis) and frequency (vertical axis). In FIG.16A, the horizontal axis represents time, and the vertical axisrepresents frequency. Transmission times t₁ to t₃ are set to the timeaxis. Herein, the same time length is set to the times t₁ to t₃respectively. Transmission frequencies f₁ to f₅ are set to the frequencyaxis. Herein, a same frequency range F_(c) is set to the frequencies f₁to f₅. With reference to the transmission times t₁ to t₃ and thetransmission frequencies f₁ to f₅, fifteen chunks K₁ to K₁₅ are set asshown in FIG. 16A.

Furthermore, five chunks K₁ to K₅ are connected as shown in FIG. 16B andare then equally divided into six slots along the time axis, thussetting communication slots s₁ to s₆ each of which has a time length oft₁/6 and a frequency range of 5f₁. The communication slots s₁ and s₄ areassigned to a first user; the communication slots s₂ and s₅ are assignedto a second user; and the communication slots s₃ and s₆ are assigned toa third user. This makes it possible for the first to third users toobtain frequency diversity effects.

Next, the chunk K₁₀ is assigned to a fourth user as a communication slots₁₁. The chunks K₇, K₈, and K₉ are connected so as to form communicationslots s₈ to s₁₀, each of which has a time length of t₂ and a frequencyrange of 3f₁ and which are assigned to a fifth user. Furthermore, thechunk K₆ is assigned to a sixth user as a communication slot s₇. Thismakes it possible for the fourth to sixth users to obtain multiuserdiversity effects, and this makes it possible for the fifth user toobtain a frequency diversity effect.

Furthermore, the chunk K₁₁ is assigned to a seventh user as acommunication slot s₁₂. This makes it possible for this user to obtain amultiuser diversity effect. Furthermore, the chunks K₁₃ and K₁₅ areassigned to an eighth user as communication slots s₁₉ and s26. Thismakes it possible for this user to obtain a multiuser diversity effect.

Furthermore, the two chunks K₁₂ and K₁₄ are equally divided into sixslots, thus forming slots s₁₃ to s₁₈ and s₂₀ to s₂₅. The communicationslots s₁₃, s₁₆, S₂₀, and s₂₃ are assigned to a ninth user; thecommunication slots s₁₄, s₁₇, s₂₁, and s₂₄ are assigned to a tenth user;and the communication slots s₁₅, s₁₈, s₂₂, and s₂₅ are assigned to aneleventh user. This makes it possible for the ninth to eleventh users toobtain frequency diversity effects individually.

-   Non-patent document 1: Contribution to 3GPP, R1-050249, “Downlink    Multiple Access Scheme for Evolved UTRA”, [Retrieval on Aug. 17,    2005], Internet (URL:    ftp://ftp.3gpp.org/TSG_RAN/WG1_RL1/TSGR1_(—)40bis/Docs/R1-050249.zip)    Non-patent document 2: Contribution to 3GPP, R1-050590, “Physical    Channels and Multiplexing in Evolved UTRA Downlink”, [Retrieval on    Aug. 17, 2005], Internet (URL:    ftp://ftp.3gpp.org/TSG_RAN/WG1_RL1/R1_Ad_Hocs/LTE_AH_June-05/Docs/R1-050590.zip)

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In order to obtain frequency diversity effects in the aforementionedconventionally-known methods, it is necessary to increase spreadcoefficients or to reduce coding coefficients in error correcting codingin response to frequency variations of transfer functions in propagationpaths.

FIGS. 17A and 17B and FIGS. 18A and 18B are graphs showing delayprofiles and transfer functions with regard to signals that arepropagated through plural propagation paths having different delay timesso as to reach wireless reception devices.

FIGS. 17A and 18A show delay profiles showing transmission signals,which are propagated through plural propagation paths so as to reach awireless reception device, with respect to time (horizontal axis) andpower (vertical axis). FIGS. 17B and 18B show transfer functions forperforming frequency conversion on delay profiles with respect tofrequency (horizontal axis) and power (vertical axis).

FIG. 17A shows the appearance of six delay waveforms w11 to w16, andFIG. 18A shows the appearance of three delay waveforms w21 to w23. Theydiffer from each other with respect to maximum delay times t1 and t2.

When the maximum delay time t1 is long as shown in FIGS. 17A and 17B,i.e., when relatively rapid frequency variations (rapid power variationsin the frequency direction) occur in the transfer function, it isexpected to produce an adequate frequency diversity effect irrespectiveof a small spread coefficient and a high coding coefficient in errorcorrecting coding. However, when the maximum delay time t2 is small asshown in FIGS. 18A and 18B, i.e., when relatively moderate frequencyvariations occur in the transfer function, it is not expected to producean adequate frequency diversity effect when the spread coefficient issmall and the coding coefficient in error correcting coding is high;hence, it is necessary to increase the spread coefficient and to reducethe coding coefficient in error correcting coding.

D1 and D2 in FIG. 17B and FIG. 18B show signals, i.e., data. That is, inFIG. 17B, a spread ratio of the spectrum spreading technology is set to“4” with respect to data D1 and D2, thus assigning four sub-carriers a₁₁to a₁₄ to the data D1. Similarly, four sub-carriers a₁₅ to a₁₈ areassigned to the data D2. In this case, the transfer function has rapidfrequency variations; hence, reception power of the sub-carrier a₁₃regarding the data D1 remarkably decreases, so that reception power ofthe sub-carrier a₁₆ regarding the data D2 remarkably decreases as well.Therefore, no reception failure occurs with respect to the data D1 andD2.

In FIG. 18B, the spread ratio is set to “8” so as to assign eightsub-carriers a₂₁ to a₂₈ to the data D1. In this case, the transferfunction has slow frequency variations so that the reception power ofthe sub-carrier a₂₄ remarkably decreases, and the reception power of thesub-carriers a₂₃ and a₂₅ slightly decreases, whereas the data spreadingratio is increased compared with the case of FIG. 17B so that noreception failure occurs with respect to the data D1. The aforementionedvalues of the spread ratios are described for the sake of convenienceand are not necessarily limited.

The present invention is made in consideration of the aforementionedcircumstances, wherein it is an object of the invention to provide awireless transmission device and a wireless transmission method that canproduce an adequate frequency diversity effect without controlling aspread coefficient and a coding coefficient in error correcting codingin the wireless transmission side.

Means for Solving the Problem

In a first aspect of the present invention, a wireless transmissiondevice includes n (where n is an integer of two or more) transmissionantennas and a delay imparting section for delaying transmission signalssupplied to the n transmission antennas by a maximum delay time (n−1)Tor less with reference to a delay time T dependent upon a communicationsignal for communicating whether the transmission signals are subjectedto frequency diversity transmission or multiuser diversity transmission.

In the wireless transmission device according to the first aspect, thedelay imparting section supplies transmission signals to only the jth(where j is an integer, 1≦j<n) transmission antenna within the ntransmission antennas when the communication signal indicates themultiuser diversity.

In the wireless transmission device according to the first aspect, inwhich a chunk, which is a basic region secured by the user to performcommunication and which is used to form regions defined by the frequencyaxis and time axis, has a frequency bandwidth F_(c), the delay impartingsection sets the delay time T such that the maximum delay time (n−1)Tbetween transmission antennas falls within a range of (n−1)T>1/F_(c)when the communication signal indicates the frequency diversity, whilethe delay imparting section sets the delay time T such that the maximumdelay time (n−1)T between transmission antennas falls within a range of(n−1)T<1/F_(c) when the communication signal indicates the multiuserdiversity.

In the wireless transmission device according to the first aspect, inwhich a chunk, which is a basic region secured by the user to performcommunication and which is used to form regions defined by the frequencyaxis and time axis, has a frequency bandwidth F_(c) and a communicationslot assigned to the user has a bandwidth BW, the delay impartingsection sets the delay time T such that the maximum delay time (n−1)Tbetween transmission antennas falls within a range of (n−1)T>1/BW whenthe communication signal indicates the frequency diversity, while thedelay imparting section sets the delay time T such that the maximumdelay time (n−1)T between transmission antennas falls within a range of(n−1)T<1/F_(c) when the communication signal indicates the multiuserdiversity.

In the wireless transmission device according to the first aspect, thedelay imparting section includes user-dependent signal processors, whichperform processing for changing the delay time T with respect to nantennas individually in response to the communication result of thecommunication signal, which performs modulation processing in units oftransmission signals with respect to users individually, and each ofwhich has n sets of delay imparting portions, and antenna-dependentsignal processors, which mixes signals output from the user-dependentsignal processors in units of n antennas.

In the wireless transmission device according to the first aspect, thedelay imparting section includes user-dependent signal processors, whichperform processing for changing a circulating delay time with respect ton antennas individually in response to the communication result of thecommunication signal, which performs modulation processing in units oftransmission signals with respect to users individually, and which has nsets of delay imparting portions, and antenna-dependent signalprocessors, which mixes signals output from the user-dependent signalprocessors in units of n antennas.

The wireless transmission device according to the first aspect includesuser-dependent signal processors for performing modulation processing inunits of transmission signals with respect to users individually, asub-carrier assignment section, which assigns sub-carriers to signalsoutput from the user-dependent signal processors in accordance withsub-carrier assignment signals, and antenna-dependent signal processorsfor performing signal processing on signals output from the sub-carrierassignment section in units of n transmission antennas; and the delayimparting section includes a phase rotation section for applyingprescribed values of phase rotation to sub-carriers individually inresponse to the communication result of the communication signal and anIFFT section for performing frequency-time conversion.

A wireless transmission device according to a second aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting and directivity controlsection, which delays transmission signals supplied to the ntransmission antennas by a maximum delay time (n−1)T or less when acommunication signal, which communicates whether transmission signalsare subjected to frequency diversity transmission or multiuser diversitytransmission, indicates frequency diversity and performs weightedmultiplication so as to control directivity when the communicationsignal indicates multiuser diversity.

The wireless transmission device according to the second aspect of thepresent invention further includes user-dependent signal processors forperforming modulation processing in units of transmission signals withrespect to users individually, a sub-carrier assignment section forassigning sub-carriers to signals output from the user-dependent signalprocessors in accordance with sub-carrier assignment signals, and aweight calculation section for calculating weights so as to controldirectivity, wherein the delay imparting and directivity control sectionincludes a weighted multiplication section for applying prescribedvalues of phase rotation to sub-carriers individually when thecommunication signal indicates the frequency diversity with respect tosignals output from the sub-carrier assignment section and forperforming multiplication using weights output from the weightedoperation section when the communication signal indicates the multiuserdiversity and an IFFT section for performing frequency-time conversion.

In the wireless transmission device according to the second aspect ofthe present invention, in which a chunk, which is a basic region securedby the user to perform communication and which is used to form regionsdefined by the frequency axis and time axis, has a frequency bandwidthF_(c), the delay imparting and directivity control section sets thedelay time T such that the maximum delay time (n−1)T betweentransmission antennas falls within a range of (n−1)T>1/F_(c) when thecommunication signal indicates frequency diversity, while it sets thedelay time T such that the maximum delay time (n−1)T betweentransmission antennas falls within a range of (n−1)T<1/F_(c) when thecommunication signal indicates multiuser diversity.

In the wireless transmission device according to the second aspect ofthe present invention, in which a chunk, which is a basic region securedby the user to perform communication and which is used to form regionsdefined by the frequency axis and time axis, has a frequency bandwidthF_(c) and a communication slot assigned to a user has a bandwidth BW,the delay imparting and directivity control section sets the delay timeT such that the maximum delay time (n−1)T between transmission antennasfalls within a range of (n−1)T>1/BW when the communication signalindicates frequency diversity, while it sets the delay time T such thatthe maximum delay time (n−1)T between transmission antennas falls withina range of (n−1)T<1/F_(c) when the communication signal indicatesmultiuser diversity.

A wireless transmission device according to a third aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting and directivity controlsection for performing weighted multiplication so as to performdirectivity control or for delaying transmission signals supplied to then transmission antennas by a maximum delay time (n−1)T or less.

In the wireless transmission device according to the third aspect of thepresent invention, in response to a communication signal for indicatingwhether transmission signals are subjected to frequency diversitytransmission or multiuser diversity transmission, the delay impartingand directivity control section delays transmission signals supplied ton transmission antennas by the maximum delay time (n−1)T or less whenthe communication signal indicates frequency diversity, while when thecommunication signal indicates multiuser diversity, it performs weightedmultiplication so as to perform directivity control, or it delaystransmission signals supplied to n transmission antennas by the maximumdelay time (n−1)T or less.

The wires transmission device according to the third aspect of thepresent invention further includes user-dependent signal processors forperforming modulation processing in units of transmission signals withrespect to users individually, a sub-carrier assignment section forassigning sub-carriers to signals output from the user-dependent signalprocessors in accordance with sub-carrier signals, and a weightcalculation section for calculating weights so as to perform directivitycontrol, wherein the delay imparting and directivity control sectionincludes a weighted multiplication section, which applies prescribedvalues of phase rotation to signals output from the sub-carrierassignment section with respect to sub-carriers individually when thecommunication signal indicates the frequency diversity, and whichperforms multiplication using weights output from the weight calculationsection and applies prescribed values of phase rotation with respect tosub-carriers when the communication signal indicates the multiuserdiversity, and an IFFT section for performing frequency-time conversionwith respect to signals output from the weighted multiplication section.

In the wireless transmission device according to the third aspect of thepresent invention, in which a chunk, which is a basic region secured bythe user to perform communication and which is used to form regionsdefined by the frequency axis and time axis, has a frequency bandwidthF_(c), the delay imparting and directivity control section sets thedelay time T such that the maximum delay time (n−1)T betweentransmission antennas falls within a range of (n−1)T>1/F_(c) when thecommunication signal indicates the frequency diversity, while it setsthe delay time T such that the maximum delay time (n−1)T betweentransmission antennas falls within a range of (n−1)T<1/F_(c) when thecommunication signal indicates the multiuser diversity and prescribedvalues of phase rotation are applied with respect to sub-carriersindividually.

In the wireless transmission device according to the third aspect of thepresent invention, in which a chunk, which is a basic region secured bythe user to perform communication and which is used to form regionsdefined by the frequency axis and time axis, has a frequency bandwidthF_(c), and a communication slot assigned to the user has a bandwidth BW,the delay imparting and directivity control section sets the delay timeT such that the maximum delay time (n−1)T between transmission antennasfalls within a range of (n−1)T>1/BW when the communication signalindicates frequency diversity, while it sets the delay time T such thatthe maximum delay time (n−1)T between transmission antennas falls withina range of (n−1)T<1/F_(c) when the communication signal indicatesmultiuser diversity and prescribed values of phase rotation are appliedwith respect to sub-carriers individually.

A wireless transmission device according to a fourth aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting section for delayingtransmission signals supplied to the n transmission antennas by amaximum delay time (n−1)T or less, wherein the delay imparting sectionsets the delay time T such that the maximum delay time (n−1)T fallswithin a range of (n−1)T<1/F_(c) when the transmission antennas transmita common pilot signal; it sets the delay time T such that the maximumdelay time (n−1)T falls within a range of (n−1)T>1/F_(c) when acommunication signal, which indicates whether a chunk including thecommon pilot signal is subjected to frequency diversity transmission ormultiuser diversity transmission, indicates frequency diversity; and itsets the delay time T such that the maximum delay time (n−1)T fallswithin a range of (n−1)T<1/F_(c) when the communication signal indicatesmultiuser diversity.

A wireless transmission device according to a fifth aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting section for delayingtransmission signals supplied to the n transmission antennas by amaximum delay time (n−1)T or less, wherein the delay imparting sectionsets the delay time T such that the maximum delay time (n−1)T fallswithin a range of (n−1)T>1/F_(c) when a communication signal, whichindicates whether a chunk including an individual pilot channel issubjected to frequency diversity transmission or multiuser diversitytransmission, indicates frequency diversity, while it sets the delaytime T such that the maximum delay time (n−1)T falls within a range of(n−1)T<1/F_(c) when the communication signal indicates multiuserdiversity.

A wireless transmission device according to a sixth aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting section for delayingtransmission signals supplied to the n transmission antennas by amaximum delay time (n−1)T or less, wherein when the transmissionantennas transmit individual pilot signals, the delay imparting sectionsets the delay time T such that the maximum delay time (n−1)T fallswithin a range of (n−1)T>1/F_(c) when a communication signal, whichindicates whether a chunk including an individual pilot channel issubjected to frequency diversity transmission or multiuser diversitytransmission, indicates frequency diversity, while it performsdirectivity control using weights output from the weight calculationsection when the communication signal indicates multiuser diversity.

A wireless transmission device according to a seventh aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting section for delayingtransmission signals supplied to the n transmission antennas by amaximum delay time (n−1)T or less, wherein when the transmissionantennas transmit individual pilot signals, the delay imparting sectionsets the delay time T such that the maximum delay time (n−1)T fallswithin a range of (n−1)T>1/F_(c) when a communication signal, whichindicates whether a chunk including an individual pilot channel issubjected to frequency diversity transmission or multiuser diversitytransmission, indicates frequency diversity, while it performsdirectivity control using weights output from the weight calculationsection, or it sets the delay time T such that the maximum delay time(n−1)T falls within a range of (n−1)T<1/F_(c) when the communicationsignal indicates multiuser diversity.

A wireless transmission device according to an eighth aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting section for delayingtransmission signals supplied to the n transmission antennas by amaximum delay time (n−1)T or less, wherein the delay imparting sectionsets the delay time T such that the maximum delay time (n−1)T fallswithin a range of (n−1)T>1/F_(c) when the transmission antennas transmitsynchronization signals.

A wireless transmission device according to a ninth aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting section for delayingtransmission signals supplied to the n transmission antennas by amaximum delay time (n−1)T or less, wherein the delay imparting sectionsets the same maximum delay time as a common pilot signal to a commoncontrol signal or an individual control signal, which is transmitted viathe transmission antennas.

A wireless transmission device according to a tenth aspect of thepresent invention includes n (where n is an integer of two or more)transmission antennas and a delay imparting section for delayingtransmission signals supplied to the n transmission antennas by amaximum delay time (n−1)T or less, wherein the delay imparting sectionsets the maximum delay time (n−1)T, being defined as (n−1)T>1/F_(c) whenthe transmission antennas transmit multicast signals or broadcastsignals.

In the wireless transmission devices according to the first to tenthaspects of the present invention, the n transmission antennas belong todifferent sectors.

In the wireless transmission devices according to the first to tenthaspects of the present invention, the n transmission antennas belong todifferent base stations.

A multicarrier wireless transmission device according to an eleventhaspect of the present invention includes n (where n is an integer of twoor more) transmission antennas and a delay imparting section forsequentially delaying transmission signals to be supplied to the ntransmission antennas, wherein the delay imparting section is capable ofvarying delay values of the transmission signals so as to produceoptimum transmission diversity effects.

A multicarrier wireless transmission device according to a twelfthaspect of the present invention includes n (where n is an integer of twoor more) transmission antennas and a delay imparting and directivitycontrol section for supplying transmission signals, which aresequentially delayed or which are subjected to directivity control byway of multiplication using prescribed weights, to the n transmissionantennas, wherein the delay imparting and directivity control sectionperforms multiplication on the delay values or the weights with respectto transmission signals, thus producing optimum transmission diversityeffects.

A multicarrier wireless transmission device according to a thirteenthaspect of the present invention includes n (where n is an integer of twoor more) transmission antennas and a delay imparting section forsequentially delaying transmission signals to be supplied to the ntransmission antennas, wherein the delay imparting section applies adelay time applied to a chunk including a common pilot channel, which istransmitted via the transmission antennas, to the common pilot channel.

A multicarrier wireless transmission device according to a fourteenthaspect of the present invention includes n (where n is an integer of twoor more) transmission antennas and a delay imparting section forsequentially delaying transmission signals to be supplied to the ntransmission antennas, wherein the delay imparting section applies adelay time applied to a chunk including an individual pilot channel,which is transmitted via the transmission antennas, to the individualpilot channel.

A multicarrier wireless transmission device according to a fifteenthaspect of the present invention includes n (where n is an integer of twoor more) transmission antennas and a delay imparting and directivitycontrol section for sequentially delaying transmission signals or forperforming directivity control by way of multiplication using prescribedweights on transmission signals to be supplied to the n transmissionantennas, wherein the delay imparting and directivity control sectionapplies a delay time applied to a chunk including an individual pilotchannel, which is transmitted via the transmission antennas, to theindividual pilot channel, or it applies an appropriate weight to theindividual pilot channel so as to perform directivity control.

A multicarrier wireless transmission device according to a sixteenthaspect of the present invention includes n (where n is an integer of twoor more) transmission antennas and a delay imparting section forsequentially delaying transmission signals to be supplied to the ntransmission antennas, wherein the delay imparting section applies delayto a synchronization signal, which is transmitted via the transmissionantennas.

A multicarrier wireless transmission device according to a seventeenthaspect of the present invention includes n (where n is an integer of twoor more) transmission antennas and a delay imparting section forsequentially delaying transmission signals to be supplied to the ntransmission antennas, wherein the delay imparting section applies adelay time applied to a common pilot channel, which is transmitted viathe transmission antennas, to one of or both of a common control signaland an individual control signal.

A multicarrier wireless transmission device according to an eighteenthaspect of the present invention includes n (where n is an integer of twoor more) transmission antennas and a delay imparting section forsequentially delaying transmission signals to be supplied to the ntransmission antennas, wherein the delay imparting section applies adelay to a multicast signal or a broadcast signal, which is transmittedvia the transmission antennas.

According to a wireless transmission method of the present invention,with reference to a delay time T suited to a communication signal, whichindicates whether transmission signals are subjected to frequencydiversity transmission or multiuser diversity transmission, thetransmission signals supplied to the n (where n is an integer of two ormore) transmission antennas are delayed by the maximum delay time (n−1)Tor less.

Effect of the Invention

With reference to the delay time T suited to the communication signal,which indicates either the frequency diversity transmission or themultiuser diversity transmission, the transmission signals supplied tothe n transmission antennas are each delayed by the delay time (n−1)T orless.

Thus, by appropriately setting the delay time T based on the conditionwhether the transmission signals are subjected to frequency diversitytransmission or multiuser diversity transmission, it is possible toproduce frequency diversity effects and multiuser diversity effectswithout being affected by the condition of a propagation path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration showing that signals transmitted by awireless transmission device according to a first embodiment of thepresent invention are propagated through plural propagation paths so asto reach a wireless reception device.

FIG. 2A is a graph showing a delay profile applied to signals that arepropagated through plural propagation paths having different delay timesso as to reach a wireless reception device.

FIG. 2B is a graph showing a transfer function that is produced byperforming frequency conversion on the delay profile shown in FIG. 2A.

FIG. 3A is a graph showing another delay profile applied to signals thatare propagated through plural propagation paths having different delaytimes so as to reach a wireless reception device.

FIG. 3B is a graph showing a transfer function of the wireless receptiondevice, which is produced by performing frequency conversion on thedelay profile shown in FIG. 3A.

FIG. 3C is a graph showing a transfer function of another wirelessreception device located at a different position, which is produced byperforming frequency conversion on the delay profile shown in FIG. 3A.

FIG. 4A is a graph showing a maximum delay time (n−1)T in a delayprofile.

FIG. 4B is a graph showing the relationship between the maximum delaytime (n−1)T shown in FIG. 4A and frequency variations.

FIG. 5A is a graph showing another maximum delay time (n−1)T in a delayprofile.

FIG. 5B is a graph showing the relationship between the maximum delaytime (n−1)T shown in FIG. 5A and frequency variations.

FIG. 6A is an illustration showing a wireless transmission/receptionsystem, in which the same signal not having a delay time is transmittedvia plural antennas of a wireless transmission device.

FIG. 6B is a graph showing an example of a reception signal in thesystem shown in FIG. 6A.

FIG. 6C is a graph showing another example of a reception signal in thesystem shown in FIG. 6A.

FIG. 7A is an illustration showing a wireless transmission/receptionsystem, in which the same signal is applied with different delay timesand is then transmitted via plural transmission antennas of a wirelesstransmission device.

FIG. 7B is a graph showing an example of a reception signal in thesystem shown in FIG. 7A.

FIG. 7C is a graph showing another example of a reception signal in thesystem shown in FIG. 7A.

FIG. 8 is a block diagram showing the configuration of a physical layerof a wireless transmission device according to a second embodiment ofthe present invention.

FIG. 9A shows an example of a signal that is produced by applying acirculating delay to a transmission signal in accordance with a thirdembodiment of the present invention.

FIG. 9B shows another example of a signal that is produced by applying acirculating delay to a transmission signal in accordance with the thirdembodiment of the present invention.

FIG. 10 is a block diagram showing the configuration of a physical layerof a wireless transmission device according to the third embodiment ofthe present invention.

FIG. 11 is an illustration for explaining operation of a circulatingdelay imparting section 119-1 in the third embodiment of the presentinvention.

FIG. 12 is a block diagram showing the configuration of a physical layerof a wireless transmission device according to a fourth embodiment ofthe present invention.

FIG. 13 is a block diagram showing the configuration of a physical layerof a wireless transmission device according to a fifth embodiment of thepresent invention.

FIG. 14 is a table showing the relationship between the maximum delaytime (n−1)T between transmission antennas and a frequency bandwidthF_(c) of a chunk with respect to each physical channel.

FIG. 15 is a table showing another relationship between the maximumdelay time (n−1)T between transmission antennas and the frequencybandwidth F_(c) of a chunk with respect to each physical channel.

FIG. 16A is a graph showing the relationship between signals, which aretransmitted from a wireless transmission device to a wireless receptiondevice, with respect to time (horizontal axis) and frequency (verticalaxis).

FIG. 16B is a graph showing communication slots that are assigned to atime-frequency space shown in FIG. 16A.

FIG. 17A is a graph showing a delay profile adapted to signals that arepropagated through plural propagation paths having different delay timesso as to reach a wireless reception device.

FIG. 17B is a graph showing a transfer function that is produced byperforming frequency conversion on the delay profile shown in FIG. 17A.

FIG. 18A is a graph showing a delay profile adapted to signals that arepropagated through propagation paths having different delay times so asto reach a wireless reception device.

FIG. 18B is a graph showing a transfer function that is produced byperforming frequency conversion on the delay profile shown in FIG. 18A.

DESCRIPTION OF THE REFERENCE NUMERALS 1 wireless transmission device 2-4transmission antenna 5, 6 delay 7, 8, 9, 10 wireless reception device11a, 11b, 111a, user-dependent signal processor 111b, 211a, 211b 12-1,12-2, 12-3, antenna-dependent signal processor 112-1 to 112-3, 212-1 to212-3, 312-1 to 312-3 13 error correcting coding section 14 modulator15, 215 sub-carrier assignment section 16 IFFT section 17parallel-series converter 18 GI imparting section 19-1 to 19-3 delayimparting section 119-1 to 119-3 circulating delay imparting section 20mixer 21 filter 22 D/A converter 110 memory 219 phase rotation section220 delay imparting section 310 weight calculation section 319 weightedmultiplication section 320 delay imparting and directivity controlsection

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

FIG. 1 is a schematic illustration showing that signals transmitted froma wireless transmission device 1 are propagated through pluralpropagation paths so as to reach a wireless reception device 7. Thewireless transmission device 1 has plural transmission antennas 2 to 4,which are respectively applied with different delay times 0, T, and 2Tand from which signals are transmitted. The wireless reception device 7receives signals transmitted from the wireless transmission device 1.FIG. 1 shows an example in which the wireless transmission device 1 isequipped with three transmission antennas 2 to 4.

Suppose that plural transmission antennas are transmission antennasinstalled in a wireless transmission device facilitated in a basestation for cellular phones, wherein three types of transmissionantennas are provided with respect to different sectors of the same basestation and with respect to different base stations. The followingdescription is given with respect to the situation in which they belongto the same sector, for example, but it is possible to employ anotherconstitution. That is, n transmission antennas belong to differentsectors, or n transmission antennas belong to different base stations.

In the figure, delays 5 and 6 apply a delay time T, by which, asdescribed above, the delay time T is applied to the transmission antenna3, and the delay time 2T is applied to the transmission antenna 4.

FIGS. 2A and 2B show a delay profile and a transfer function withrespect to signals, which are propagated through plural (three)propagation paths having different delay times so as to reach a wirelessreception device. FIG. 2A shows the delay profile showing thattransmission signals are propagated through plural propagation pathshaving different delay times so as to reach the wireless receptiondevice with respect to time (horizontal axis) and power (vertical axis).As shown in FIG. 2A, the delay profile instantaneously has a maximumdelay waveform of 2T+d_(max); hence, compared with the constitution inwhich the same signal is transmitted via each transmission antenna, themaximum delay waveform becomes very large. Herein, d_(max) represents anarrival time difference between a fast propagation path and a slowpropagation path when radio waves arrive at a reception antenna from atransmission antenna.

FIG. 2B shows a transfer function that is produced by performingfrequency conversion on the delay profile of FIG. 2A with respect tofrequency (horizontal axis) and power (vertical axis). In the delayprofile, the increasing maximum delay time 2T+d_(max) indicates rapidfrequency variations of the transfer function. Therefore, as shown inFIG. 2B (similar to FIG. 17B), data D1 and D2 are spread with a spreadratio “4” and are assigned with sub-carriers. It is preferable that thespread coefficient or the coding coefficient of error correcting codingbe controlled in response to frequency variations of the transferfunction in the wireless transmission device 1, wherein theaforementioned method states that the delay time 2T is acknowledged inadvance by the wireless transmission device 1; hence, it is possible todetermine the spread coefficient or the coding coefficient of errorcorrecting coding irrespective of frequency variations of propagationpaths.

In order to produce multiuser diversity effects, it is preferable thatthe maximum delay time 2T+d_(max), which appears instantaneously in thedelay profile, be not increased so much. Multiuser diversity effectswill be described with reference to FIGS. 3A to 3C.

FIGS. 3A to 3C show a delay profile and transfer functions with respectto signals that are propagated through plural propagation paths havingdifferent delay times so as to reach a wireless reception device. FIG.3A shows the delay profile adapted so transmission signals that arepropagated through plural (three) propagation paths having differentdelay times so as to reach the wireless reception device with respect totime (horizontal axis) and power (vertical axis).

FIG. 3B shows a transfer function with regard to a wireless receptiondevice used by a user u1. FIG. 3C shows a transfer function with regardto a wireless reception device used by a user u2. Since the wirelessreception devices of the users u1 and u2 differ from each other inlocation, the instantaneous transfer functions thereof differ from eachother.

Suppose that a left region is connected to a frequency channel b1 and aright channel is connected to a frequency channel b2 in FIGS. 3B and 3C,the user u1 enjoys a good quality in the frequency channel b2, while theuser u2 enjoys a good quality in the frequency channel b1. Therefore,data D1 to D4 are transmitted to the user u1 over the frequency channelb2. Data D1 to D4 are subjected to spectrum spreading. Data D1 to D4 aretransmitted to the user u2 over the frequency channel b1. In this case,data D1 to D4 are subjected to spectrum spreading.

As described above, by use of a quality difference between frequencychannels at a certain instant, it is possible to produce multiuserdiversity effects for improving transmission efficiency with respect todifferent users who perform communications using different frequencychannels.

However, when the maximum delay time 2T+d_(max) is increased so much,rapid frequency variations occur in the transfer function, thus reducingquality difference between the frequency channel b1 and the frequencychannel b2.

Therefore, in order to produce adequate multiuser diversity effects, itis important to reduce the maximum delay time 2T+d_(max) as shown inFIG. 3A.

FIGS. 4A and 4B and FIGS. 5A and 5B show the relationships between themaximum delay time (n−1)T and frequency variations. When an arrival timedifference (n−1)T appears between arrival waves w31 and w32 as shown inFIG. 4A, a transfer function of this propagation path is shown in FIG.4B. That is, a frequency difference between amplitude drops of power(vertical axis) is defined as F=1/(n−1)T.

When plural delay waves w41 to w43 appear as shown in FIG. 5A, anarrival time difference (n−1)T appears between the first arrival wavew41 and the last arrival wave w43, so that a frequency differencebetween amplitude drops of power (vertical axis) is defined asF=1/(n−1)T as shown in FIG. 5B.

In this connection, the frequency diversity effect differs from themultiuser diversity effect in terms of frequency variations ofappropriate transfer functions thereof; hence, in order to produce thefrequency diversity effect, the maximum delay time (n−1)T is set as(n−1)T>F_(c) where F_(c) denotes a frequency bandwidth of a chunk, whichis a basic region secured by the user to perform communication anddefined with respect to the frequency axis and time axis, thus creatingan environment easily producing the frequency diversity effect.

In contrast, in order to produce the multiuser diversity effect, themaximum delay time (n−1)T is set as (n−1)T<1/F_(c), where F_(c) denotesa frequency bandwidth of a chunk, thus creating an environment easilyproducing the multiuser diversity effect. In the following description,an inequality of (n−1)T<1/F_(c) encompasses (n−1)T=0. In the followingdescription, delay times applied to transmission antennas are eachrepresented as (n−1) multiples of T where T is assumed to be constant,whereas it is possible to change T with respect to each of transmissionantennas. In order to produce the multiuser diversity effect, it ispossible to reduce the maximum delay time by reducing the number oftransmission antennas used for transmission instead of setting theinequality of (n−1)T<1/F_(c).

As described above, in response to a determination as to whethertransmission signals are subjected to the frequency diversitytransmission or the multiuser diversity transmission (i.e.,(n−1)T>1/F_(c) or (1−n)T<1/F_(c)), it is possible to produce thefrequency diversity effect or the multiuser diversity effect withoutbeing affected by conditions of propagation paths.

As shown in FIG. 16A, with respect to the first user who performscommunication by way of the communication slot s₁ that is produced byconnecting plural consecutive chunks in the frequency direction and theuser who is assigned with discontinuous chunks such as the ninth userwho is assigned with the communication slots s₁₃, s₁₆, s₂₀, and s₂₃, thebandwidth BW (i.e., BW=5F for the first user, and BW=3F for the ninthuser) of a communication slot instantaneously assigned to the userdefines the basis for the realization of the frequency diversity effect;hence, by setting the maximum delay time as (n−1)T>1/BW, it is possibleto produce the frequency diversity effect.

For example, the delay time T is set such that the maximum delay time(n−1)T between transmission antennas falls within a range of (n−1)T>1/BWwhen a communication signal indicates the frequency diversity effect,while the delay time T is set such that the maximum delay time (n−1)Tbetween transmission antennas falls within a range of (n−1)T<1/F_(c).

Although no illustration is provided, when a sub-carrier partiallyincluded in plural chunks is assigned to a certain user, the bandwidthBW of a communication slot assigned to the user represents a frequencydifference between the sub-carriers, which deviate from each other atmost within the sub-carriers instantaneously assigned to the user.

The determination as to whether signals are subjected to the frequencydiversity transmission or the multiuser diversity transmission can bechanged over based on types of transmission signals (e.g., pilotsignals, control signals, broadcast/multicast signals, and the like),moving speeds of wireless reception devices (where the frequencydiversity is selected in case of a high moving speed, and the multiuserdiversity is selected in case of a low moving speed), and the like.

FIGS. 6A to 6C are explanatory drawings for the situation in which thesame signal having no delay time is transmitted via plural antennas of awireless transmission device 8. Suppose that, as shown in FIG. 6A, thewireless transmission device 8 is equipped with plural (three)transmission antennas, which are arranged in parallel and which have nodirectivity in the horizontal direction. Due to the occurrence of lobese11 and e12 indicated by ellipses shown in FIG. 6A, there is a directionarranging a wireless reception device 9 that receives reception signalswith a high reception level with respect to all frequency bands (seeFIG. 6B) and a direction arranging a wireless reception device 10 thatreceives reception signals with a low reception level with respect toall frequency bands (see FIG. 6C).

FIGS. 7A to 7C are explanatory drawings in which the same signal isapplied with different delay times respectively and is then transmittedvia plural transmission antennas of the wireless transmission device 8.Suppose that the wireless transmission device 8 is equipped with plural(three) transmission antennas having no directivity, which are arrangedin parallel. Due to the occurrence of lobes e21 to e26 in narrow bands,there occur a frequency band securing a high reception level and afrequency band securing a low reception level within reception signals,whereas an average reception level is maintained substantially constantirrespective of directions; hence, it is possible to securesubstantially the same quality with respect to both of the receptionlevel of a wireless reception device 9 (see FIG. 7B) and the receptionlevel of a wireless reception device 10 (see FIG. 7C). Therefore, themethod, in which signals are applied with different delay times and arethen transmitted via transmission antennas of the wireless transmissiondevice 8, compensates for drawbacks of the method, which is describedwith reference to FIGS. 6A to 6C and in which the same signal istransmitted via plural transmission antennas.

Second Embodiment

A second embodiment of the present invention will be described withrespect to the constitution of a wireless transmission device. Similarto the wireless transmission device 1 of the first embodiment (see FIG.1), the wireless transmission device of the present embodiment hasplural transmission antennas.

The wireless transmission device described below is a wirelesstransmission device in which different delay times are applied totransmission antennas for transmitting signals, wherein delay times areimparted in a time region.

Signals applied with different delay times in connection withtransmission antennas are described in the present embodiment in such away that a signal, which is delayed by T with respect to a transmissionsignal actually transmitted from a first transmission antenna, istransmitted via a second transmission antenna, and similarly, a n-thtransmission antenna transmits a signal delayed by (n−1)T.

FIG. 8 is a block diagram showing the configuration of a physical layerof the wireless transmission device of the present embodiment. Thephysical layer represents a portion of the configuration of the wirelesstransmission device, in particular, which receives transmission signals,which performs signal processing into a wireless-transmittable form, andwhich forwards signals to a wireless frequency converter for performingfrequency conversion into wireless frequencies.

As shown in FIG. 8, the physical layer includes user-dependent signalprocessors 11 a and 11 b and antenna-dependent signal processors 12-1,12-2, and 12-3. The user-dependent signal processor 11 a (similar to theuser-dependent signal processor 11 b) performs signal processing onsignals to be transmitted to a wireless reception device used by eachuser. The antenna-dependent signal processor 12-1 (similar to theantenna-dependent signal processors 12-2 and 12-3) performs signalprocessing with respect to each of transmission antennas.

The user-dependent signal processor 11 a includes an error correctingcoding section 13, a modulator 14, a sub-carrier assignment section 15,an IFFT (Inverse Fast Fourier Transform) section 16, a parallel-seriesconversion section 17, a GI (Guard Interval) imparting section 18, anddelay imparting sections 19-1, 19-2, and 19-3.

The error correcting coding section 13 performs error correcting codingon transmission signals. The modulator 14 performs modulation processingsuch as QPSK (Quadrature Phase Shift Keying) and 16QAM (QuadratureAmplitude Modulation) on the output of the error correcting codingsection 13.

The sub-carrier assignment section 15 assigns the output of themodulator 14 to appropriate sub-carriers based on sub-carrier assignmentinformation indicated by a high-order layer. The IFFT section 16performs frequency-time conversion on the output of the sub-carrierassignment section 15.

The parallel-series conversion section 17 performs parallel-seriesconversion on the output of the IFFT section 16. The GI impartingsection 18 imparts guard intervals to the output of the parallel-seriesconversion section 17. The delay imparting section 19-1 impartsdifferent delays to the output of the GI imparting section 18 inconnection with transmission antennas.

The outputs of the delay imparting sections 19-1 to 19-3 are supplied tothe antenna-dependent signal processors 12-1, 12-2, and 12-3respectively. The delay imparting sections 19-1 to 19-3 providedifferent delays (e.g., 0, S, and 2S). Herein, S=T/(sample time). Thesample time represents a minimum time interval between digital signals,which are processed in the GI imparting section 18, the delay impartingsections 19-1 to 19-3, and the mixing section 20.

Therefore, imparting a delay of S samples in the delay impartingsections 19-1 to 19-3 indicates that a delay of time T is imparted atthe output terminal of the D/A converter 22. The user-dependent signalprocessor 11 a is used in a certain chunk; in other words, it is used ineither a frequency diversity region or a multiuser diversity region;hence, it receives a communication signal (frequency div/multiuser divcommunication signal) directing the use of either the frequencydiversity region or the multiuser diversity region from the high-orderlayer controlling the physical layer. The user-dependent signalprocessor 11 a selectively uses either the frequency diversity region orthe multiuser diversity region based on the communication signal, thusfunctioning to change the delay time T.

The user-dependent signal processor 11 b has a constitution similar tothat of the user-dependent signal processor 11 a, but differs from it interms of the user thereof.

The antenna-dependent signal processor 12-1 includes the mixing section20, a filter 21, and a D/A (Digital/Analog) converter 22.

The mixing section 20 adds together and mixes signals, which are outputto the antenna-dependent signal processor 12-1 from the user-dependentsignal processors 11 a and 11 b. The filter 21 extracts signals of aprescribed band only from the output of the mixing section 20. The D/Aconverter 22 performs digital-to-analog conversion on the output of thefilter 21.

Both the antenna-dependent signal processors 12-2 and 12-3 have theconstitution similar to that of the antenna-dependent signal processor12-1. The output of the antenna-dependent signal processor 12-1 isforwarded to a wireless frequency converter (not shown) for performingfrequency conversion into wireless frequencies, from which it issupplied to plural (three) transmission antennas, thus transmittingwireless signals.

Third Embodiment

A third embodiment of the present invention will be described withrespect to another constitution of a wireless transmission device. Thewireless transmission device of the present embodiment is a wirelesstransmission device that applies different delay times to transmissionantennas so as to transmit signals, wherein delay times are applied withrespect to a time region.

The wireless transmission device handles signals, which are applied withguard intervals with respect to symbols (valid symbol intervals) oftransmission signals. Signals applied with different delay times withrespect to transmission antennas are focused on prescribed portions(valid symbol intervals) of transmission signals, which are actuallytransmitted via a first transmission antenna except for guard intervals;hence, only the valid symbol intervals are delayed by T and are thentransmitted via a second transmission antenna; similarly, only the validsymbol intervals are delayed by (n−1)T and are then transmitted via an-th transmission antenna.

Therefore, transmission antennas transmit signals, which are appliedwith guard intervals in correspondence with valid symbol intervals;hence, unlike the second embodiment, no time deviation occurs at thesymbol timing at the transmission antennas. A delay time impartingmethod described above is referred to as “circulating delay imparting”in the following description. By way of the processing for impartingcirculating delay, securing delay waves is advantageous in comparisonwith the second embodiment which describes that delay times are appliedto transmission antennas.

FIGS. 9A and 9B show examples of signals that are produced by impartingcirculating delays to transmission signals in the present embodiment.FIG. 9A shows a signal transmitted via a first antenna, and FIG. 9Bshows a signal transmitted via a second antenna. FIGS. 9A and 9B showthat the valid symbol interval corresponds to four samples and the guardinterval corresponds to one sample, wherein with regard to the validsymbol interval, one sample is delayed in the second antenna comparedwith the first antenna. No symbol timing deviation occurs in units ofsymbols with respect to the first antenna and the second antenna; hence,even when a circulating delay is applied thereto, it is acknowledgedthat a guard interval effect for intensifying against interferences withadjacent symbols is maintained.

FIG. 10 is a block diagram showing the configuration of the physicallayer of the wireless transmission device according to the presentembodiment. As shown in the figure, the physical layer includesuser-dependent signal processors 111 a and 111 b and antenna-dependentsignal processors 112-1, 112-2, and 112-3.

The user-dependent signal processor 111 a (similar to the user-dependentsignal processor 111 b) performs signal processing in connection with awireless transmission device used by each user. The antenna-dependentsignal processor 112-1 (similar to the antenna-dependent signalprocessors 112-2 and 112-3) performs signal processing with regard to aprescribed transmission antenna.

The constitution of the user-dependent signal processor 111 a issubstantially identical to the constitution of the user-dependent signalprocessor 11 a (FIG. 8) described in the second embodiment, whereas adifference therebetween lies in that the GI imparting section 18 is notprovided, and circulating delay imparting sections 119-1 to 119-3 areprovided instead of the delay imparting section 19-1 to 19-3.

The user-dependent signal processor 111 a shares the same functions asthe error correcting coding section 13, the modulator 14, thesub-carrier assignment section 15, the IFFT section 16, and theparallel-series conversion section 17 incorporated in the secondembodiment (see FIG. 8); hence, they are designated by the samereference numerals, and the description thereof will be omitted.

The circulating delay imparting section 119-1 imparts differentcirculating delays to the output of the parallel-series conversionsection 17 in connection with transmission antennas. The outputs of thecirculating delay imparting sections 119-1 to 119-3 are supplied to theantenna-dependent signal processors 112-1, 112-2, and 112-3. Inaddition, the circulating delay imparting sections 119-1 to 119-3provide different delays (e.g., 0, S, and 2S). Herein, S=T/(sampletime).

The user-dependent signal processor 111 a is used in a certain chunk.Since it is used in either the frequency diversity region or themultiuser diversity region, it receives a communication signal directingthe use of either the frequency diversity region or the multiuserdiversity region by means of the high-order controlling the physicallayer. The user-dependent signal processor 111 a selectively uses eitherthe frequency diversity region or the multiuser diversity region basedon the communication signal, thus functioning to change the delay timeT.

The user-dependent signal processor 111 b has a similar constitution asthe user-dependent signal processor 111 a, but differs from it in termsof the user.

FIG. 11 is an illustration for explaining the circulating delayimparting section 119-1, which is described as an example of the presentembodiment. The circulating delay imparting section 119-1 is equippedwith a memory 110. In order to impart a circulating delay of k samples,data D11 is sequentially input into address k+1 to address n of thememory 110 (i.e., 1, 2, 3, . . . , (n−k) are input); then, a subsequenceof the data D11 is input at address 1 (i.e., (n−k+1), (n−k+2), (n−k+3),. . . , n) are input), thus inputting n samples of the data D11. Next,by sequentially outputting from address 1 of the memory 110, it ispossible to output data D12, which is produced by imparting acirculating delay of k samples to the n samples of the data D11, (i.e.,(n−k+1), (n−k+2), (n−k+3), n, 1, 2, . . . , (n−k)).

FIG. 9A shows an example of the signal, which is produced by imparting acirculating delay of zero sample to data of four samples, and FIG. 9Bshows an example of the signal, which is produced by imparting acirculating delay of one sample.

The constitution of the antenna-dependent signal processor 112-1 (FIG.10) is substantially identical to the constitution of theantenna-dependent signal processor 12-1 (FIG. 8) described in the secondembodiment, wherein a difference therebetween lies in that the GIimparting section 18 is provided therefor.

Functions of the mixing section 20, the GI imparting section 18, thefilter 21, and the D/A converter 22 included in the antenna-dependentsignal processor 112-1 are identical to those incorporated in the secondembodiment (FIG. 8); hence, they are designated by the same referencenumerals, and the description thereof will be omitted.

Both the antenna-dependent signal processor 112-2 and 112-3 have aconstitution similar to that of the antenna-dependent signal processor112-1. The outputs of the antenna-dependent signal processors 112-1,112-2, and 112-3 are supplied to a wireless frequency converter (notshown) for performing frequency conversion into wireless frequencies,from which they are supplied to plural (three) transmission antennas,thus transmitting wireless signals.

Fourth Embodiment

A fourth embodiment of the present invention will be described withreference to the constitution of another wireless transmission device.The wireless transmission device of the present embodiment is a wirelesstransmission device in which different delay times are applied totransmission antennas so as to transmit signals, wherein delay times areapplied with respect to a frequency region.

The present embodiment deals with signals that are applied with guardintervals with respect to symbols (valid symbol intervals) oftransmission signals, wherein similar to the wireless transmissiondevice of the third embodiment (FIG. 10), circulating delays areimparted thereto.

FIG. 12 is a block diagram showing the configuration of the physicallayer of the wireless transmission device of the present embodiment. Asshown in the figure, the physical layer includes user-dependent signalprocessors 211 a and 211 b, a sub-carrier assignment section 215, andantenna-dependent signal processors 212-1, 212-2, and 212-3.

The user-dependent signal processor 211 a (similar to the user-dependentsignal processor 211 b) performs signal processing with respect to awireless transmission device used by each user. The sub-carrierassignment section 215 assigns the output of the user-dependent signalprocessor 211 a to each sub-carrier. The antenna-dependent signalprocessor 212-1 (similar to the antenna-dependent signal processors212-2 and 212-3) performs signal processing with respect to a prescribedantenna.

Each of the user-dependent signal processors 211 a and 211 b includes anerror correcting coding section 13 and a modulator 14. Functions of theerror correcting coding section 13 and the modulator 14 aresubstantially identical to those described in the second embodiment(FIG. 8); hence, they are designated by the same reference numerals, andthe description thereof will be omitted.

The outputs of the user-dependent signal processors 211 a and 211 b areassigned with appropriate sub-carriers in the sub-carrier assignmentsection 215 based on sub-carrier assignment information indicated by thehigh-order layer; then, they are supplied to the antenna-dependentsignal processors 212-1, 212-2, and 212-3.

The antenna-dependent signal processor 212-1 includes a phase rotationsection 219, an IFFT section 16, a parallel-series conversion section17, a GI imparting section 18, a filter 21, and a D/A converter 22. Thefunctions of the IFFT section 16, the parallel-series conversion section17, the GI imparting section 18, the filter 21, and the D/A converter 22are identical to those of the second embodiment (FIG. 8); hence, theyare designated by the same reference numerals, and the descriptionthereof will be omitted.

The phase rotation section 219 rotates the output of the sub-carrierassignment section 215 in phase by θ_(m) with respect to eachsub-carrier and then outputs it to the IFFT section 16. Both theantenna-dependent signal processors 212-2 and 212-3 have a constitutionsimilar to the constitution of the antenna-dependent signal processor212-1.

The outputs of the antenna-dependent signal processors 212-1, 212-2, and212-3 are supplied to a wireless frequency converter (not shown) forperforming frequency conversion into wireless frequencies, from whichthey are supplied to plural transmission antennas, thus outputtingwireless signals.

In the present embodiment, the rotation of the phase θ_(m) in the phaserotation section 219 is set to θ_(m)=2πf_(m)·(n−1)T. Herein, f_(m)denotes a frequency difference between 0-th sub-carrier and m-thsub-carrier, wherein it is defined as f_(m)=m/Ts, so that (n−1)Trepresents a circulating delay time at n-th antenna in connection with afirst antenna. Ts represents a valid symbol time for an OFDM symbol.

A delay imparting section 220 is constituted by the phase rotationsection 219 and the IFFT section 16. The phase rotation applied by thephase rotation section 219 is subjected to frequency-time conversion inthe IFFT section 16, so that it is regarded as a time delay at theoutput of the IFFT section 16.

The user-dependent signal processor 211 a is used in a certain chunk,which is used in either the frequency diversity region or the multiuserdiversity region, wherein it receives a communication signal indicatingwhether to use the frequency diversity region or the multiuser diversityregion from the high-order layer controlling the physical layer. Basedon the communication signal, the user-dependent signal processor 211 aselectively uses the frequency diversity region or the multiuserdiversity region, thus functioning to change the delay time T.

The wireless transmission devices according to the second to fourthembodiments are each equipped with a delay imparting section fordelaying transmission signals supplied to n (n is an integer of two ormore) transmission antennas by the maximum delay time (n−1)T inaccordance with the delay time T suited to a communication signalindicating whether transmission signals are subjected to the frequencydiversity transmission or the multiuser diversity transmission.

Thus, by appropriately setting the delay time T based on thedetermination as to whether transmission signals are subjected to thefrequency diversity transmission or the multiuser diversitytransmission, it is possible to produce the frequency diversity effectand the multiuser diversity effect without being affected by conditionsof propagation paths.

Fifth Embodiment

A fifth embodiment of the present invention will be described withrespect to the constitution of another wireless transmission device. Thewireless transmission device of the present embodiment is a wirelesstransmission device that applies different delay times to signals, whichare then transmitted via transmission antennas, in the frequencydiversity region while applying appropriate weights to transmissionantennas so as to perform directivity control in the multiuser diversityregion, wherein delay times are applied and directivity control isperformed in the frequency region.

The present embodiment deals with signals that are produced by impartingguard intervals to transmission signals with respect to symbols (validsymbol intervals), wherein, similar to the third and fourth embodiments,it imparts circulating delays to signals.

FIG. 13 is a block diagram showing the configuration of a physical layerof the wireless transmission device of the present embodiment. As shownin the figure, the physical layer includes user-dependent signalprocessors 211 a and 211 b, a sub-carrier assignment section 215, aweight calculation section 310, and antenna-dependent signal processors312-1, 312-2, and 312-3. The constitutions of the user-dependent signalprocessor 211 a and the sub-carrier assignment section 215 are similarto those of the fourth embodiment (FIG. 12); hence, they are designatedby the same reference numerals, and the description thereof will beomitted.

The antenna-dependent signal processor 312-1 (similar to theantenna-dependent signal processors 312-2 and 312-3) performs signalprocessing with respect to a prescribed transmission antenna.

The antenna-dependent signal processor 312-1 includes a weightedmultiplication section 319, an IFFT section 16, a parallel-seriesconversion section 17, a GI imparting section 18, a filter 21, and a D/Aconverter 22. Functions of the IFFT section 16, the parallel-seriesconversion section 17, the GI imparting section 18, the filter section21, and the D/A converter 22 are identical to those of the firstembodiment; hence, they are designated by the same reference numerals,and the description thereof will be omitted.

The weighted multiplication section 319 performs weighted multiplicationon the output of the sub-carrier assignment section 215 with respect tosub-carriers, and outputs the results to the IFFT section 16. Both theantenna-dependent signal processors 312-2 and 312-3 have a constitutionsimilar to that of the antenna-dependent signal processor 312-1.

The outputs of the antenna-dependent signal processors 312-1, 312-2, and312-3 are supplied to a wireless frequency converter (not shown) forperforming frequency conversion into wireless frequencies, from whichthe results are supplied to transmission antennas, thus outputtingwireless signals.

A specific sub-carrier is used in a certain chunk. That is, it is usedin either the frequency diversity region or the multiuser diversityregion. The weighted multiplication section 319 is informed of thedetermination as to whether to use either the frequency diversity regionor the multiuser diversity region from the high-order layer controllingthe physical layer, based on which phase rotation θ_(m) is introduced inorder to apply different delay times to antennas in the frequencydiversity region, while multiplication using a weight w_(m) is performedin order to perform directivity control in the multiuser diversityregion.

A delay imparting and directivity control section 320 is constituted bythe weighted multiplication section 319 and the IFFT section 16. Whenphase rotation is introduced by means of the weighted multiplicationsection 319, it is regarded as a time at the output of the IFFT section16 since the IFT section 16 performs frequency-time conversion. On theother hand, when the weighted multiplication section performsmultiplication using the weights w_(m), the IFFT section 16 performsfrequency-time conversion so that the output of the IFFT section 16output from the transmission antenna is subjected to directivitycontrol.

When the weighted multiplication section 319 rotates the phase by θ_(m),similar to the fourth embodiment, it sets θ_(m)=2πf_(m)·(n−1)T. Herein,f_(m) denotes a frequency difference between the 0-th sub-carrier andthe m-th sub-carrier, wherein f_(m)=m/T_(s); and (n−1)T represent acirculating delay time at an n-th antenna in connection with a firstantenna. T_(s) represents a valid symbol time for an OFDM symbol.

In order to perform multiplication using the weight w_(m), the followingweight is set up so as to perform directivity control. Assuming a lineararray of n antennas whose distance is a half of a wavelength of acarrier frequency, the weight w_(m), is calculated in accordance withthe following equation (1):

$\begin{matrix}{w_{m} = {\frac{1}{\sqrt{n}}\left\{ {{\mathbb{e}}^{{jk}\;{{\pi sin\theta}{({0 - \frac{n - 1}{2}})}}},{\mathbb{e}}^{{jk}\;{{\pi sin\theta}{({1 - \frac{n - 1}{2}})}}},\ldots\mspace{14mu},{\mathbb{e}}^{{jk}\;{{\pi sin\theta}{({{({n - 1})} - \frac{n - 1}{2}})}}}} \right\}}} & (1)\end{matrix}$

The weight w_(m), represents a vector of a weight used in the weightedmultiplication section 319, wherein in the equation (1), the first tolast terms describe the weights used in first to n-th antennas.

In the equation (1) expressing the weight w_(m), n denotes the number ofantennas, wherein in the present embodiment, n=3; θ denotes a directionin which a main beam is directed; and k denotes a ratio between thefrequency used for transmission and the frequency that is measured basedon θ.

With respect to the main beam direction θ, a measured value produced bythe wireless transmission device or a terminal of a counter-communicatoris supplied to the weight calculation section 310, in which it is usedfor calculation of the weight w_(m). The equation (1) presents anexample of calculation for the weight w_(m), which can be calculated byway of another method. The calculation methods regarding θ and w_(m) aredescribed in “Technical Report RCS2004-229” (published by the CorporateInstitute of Electronic Information and Telecommunication on November,2004) and the like.

The delay imparting and directivity control section 320 imparts a delayof the maximum delay time (n−1)T or less between transmission antennaswhen the communication signal indicates frequency diversity, while itperforms multiplication to produce the weight w_(m) so as to performdirectivity control when the communication signal indicates multiuserdiversity.

As described in the first embodiment, the delay imparting anddirectivity control section 320 sets the delay time T such that themaximum delay time (n−1)T between transmission antennas falls within arange of (n−1)T>1/F_(c) when the communication signal indicatesfrequency diversity.

As described in the first embodiment, the delay imparting anddirectivity control section 320 sets the delay time T such that themaximum delay time (n−1)T falls within a range of (n−1)T>1/BW when thecommunication signal indicates frequency diversity.

The aforementioned description teaches that the weighted multiplicationsection 319 of the delay imparting and directivity control section 320is instructed by the high-order layer controlling the physical layer touse either the frequency diversity region or the multiuser diversityregion, based on which it applies a phase rotation θ_(m) so as to impartdifferent delay times to antennas in the frequency diversity region,while it performs multiplication to produce the weight w_(m) so as toperform directivity control in the multiuser diversity region; however,it is possible to use another method for using both the phase rotationθ_(m) and weight w_(m) in the multiuser diversity region in such a waythat, as described in the fourth embodiment, the phase rotation θ_(m) isimparted with respect to both the frequency diversity region and themultiuser diversity region before the main beam direction θ is produced,and then the directivity control is performed using the weight w_(m)after the main beam direction θ is produced in the multiuser diversityregion. Similar to the fourth embodiment, the delay time T varies inconnection with θ_(m) in accordance with the frequency diversity regionand the multiuser diversity region. Thus, in the stage before the mainbeam direction θ is produced, it is possible to produce the samemultiuser diversity effect as the fourth embodiment, while after themain beam direction θ is produced, it is expected to produce a highermultiuser diversity effect by strictly performing directivity controlusing the weight w_(m). Furthermore, by using the configuration of thephysical layer of the wireless transmission device shown in FIG. 13rather than the fourth embodiment, it is possible to realize theimprovement of characteristics due to the directivity control byslightly increasing the circuit constitution.

As described above, the delay imparting and directivity control section320 imparts a delay of the maximum delay time (n−1)T or less betweentransmission antennas when the communication signal indicates frequencydiversity, while it imparts a delay of the maximum delay time (n−1)T orless between transmission antennas, or it performs multiplication toproduce the weight w_(m) so as to perform directivity control when thecommunication signal indicates multiuser diversity.

The wireless transmission device performing the aforementionedprocessing has the constitution shown in FIG. 13, wherein, when thecommunication signal indicates the multiuser diversity, the delayimparting and directivity control section imparts a delay of the maximumdelay time (n−1)T or less between transmission antennas, or it performsmultiplication to produce the weight w_(m) so as to perform directivitycontrol.

As described in the first embodiment, the delay imparting anddirectivity control section sets the delay time T such that the maximumdelay time (n−1)T between transmission antennas falls within a range of(n−1)T>1/F_(c) when the communication signal indicates frequencydiversity, while it sets the delay time T such that the maximum delaytime falls within a range of (n−1)T<1/F_(c) when the communicationsignal indicates multiuser diversity so that a delay is applied betweentransmission antennas.

As described in the first embodiment, the delay imparting anddirectivity control section sets the delay time T such that the maximumdelay time (n−1)T between transmission antennas falls within a range of(n−1)T>1/BW when the communication signal indicates the frequencydiversity.

The aforementioned second to fifth embodiments are described withrespect to the case in which the number of users is two and the numberof antennas is three, whereas the number of users and the number ofantennas are not necessarily limited to these numbers.

In the aforementioned fourth and fifth embodiments, it is possible totransmit signals, which are subjected to multiplication using specificscramble codes dependent upon antennas, sectors, and base stations, totransmission antennas.

Sixth Embodiment

The present embodiment will be described with respect to variations ofthe maximum delay time (n−1)T dependent upon physical channels. Theaforementioned first to fifth embodiments are described under thepresumption that one-to-one communication is performed with regard toone certain chunk at certain instant, wherein (n−1)T>1/F_(c) is set toproduce the frequency diversity effect, while (n−1)T<1/F_(c) is set toproduce the multiuser diversity effect.

Normally, in communications other than one-to-one communication, a knownsignal referred to as a pilot channel is transmitted to a wirelesstransmission device in order to estimate a propagation path;alternatively, a control channel is used to inform various types ofparameters before data communication. The present embodiment will bedescribed with respect to a setup method of the maximum delay time(n−1)T in theses physical channels.

In Evolved UTRA & UTRAN examined in 3GPP (3rd Generation PartnershipProject), there are provided common pilot channels DCPCH (DownlinkCommon Pilot Channel), dedicated pilot channels DDPCH (DownlinkDedicated Pilot Channel), downlink synchronization channels DSCH(Downlink Synchronization Channel), common control channels DCCCH(Downlink Common Control Channel), downlink shared control signalingchannels DSCSCH (Downlink Shared Control Channel), andmulticast/broadcast channels (Multicast/Broadcast Channel).

Common pilot channels DCPCH correspond to pilot channels CPICH in W-CDMA(Wideband Code Division Multiple Access), which are used for theestimation of conditions of downlink propagation paths, cell search, andmeasurement of losses of propagation paths in uplink transmission powercontrol in AMCS (Adaptive Modulation and Coding Scheme).

Dedicated pilot channels DDPCH are used to perform transmission towardindividual mobile stations via transmission antennas such as adaptivearray antennas whose propagation paths (directivities) differ from thoseof cell shared antennas; alternatively, they can be used for the purposeof reinforcing downlink shared common pilot channels DSPCH in connectionwith mobile stations having low reception qualities.

Downlink synchronization channels DSCH correspond to synchronizationchannels SCH in W-CDMA, wherein they are used for cell search of mobilestations, wireless frames of OFDM (Orthogonal Frequency DivisionMultiplexing) signals, time slots, transmission timing intervals TTI(Transmission Timing Interval), and OFDM symbol timing synchronization.

Common control channels DCCCH include common control information such asbroadcast information (corresponding to broadcast channels BCH)corresponding to primary common control physical channels P-CCPCH,secondary common control physical channels S-CCPCH, and paging indicatorchannels PICH in W-CDMA, packet paging indicator PI information(corresponding to paging indicator channels PICH) designating occurrenceof packet calls, packet paging information (corresponding to pagingchannels PCH) corresponding to packet calls, and downlink accessinformation (corresponding to downlink access channels FACH).

Downlink shared control signaling channels DSCSCH correspond to HS-DSCHconnected shared control channels HS-SCCH, downlink dedicated controlchannels DPCCH, acquisition indicators AICH included in high-speedphysical downlink shared channels HS-PDSCH in HSPDA (High Speed DownlinkPacket Access), wherein they are shared by plural mobile stations andare used for transmission of the information (modulation methods, spreadcoding, etc.) that is necessary for mobile stations to performdemodulation with regard to high-speed downlink shared channels HS-DSCH,the information that is necessary for error correcting decoding and HARQprocessing, and the scheduling information of wireless resources(frequency, time).

Downlink shared data channels DSDCH correspond to high-speed downlinkshared channels HS-DSCH and downlink dedicated data channels DPDCHincluded in high-speed physical downlink shared channels HS-PDSCH inHSPDA, wherein they are used for transmission of packet data towardsmobile stations from high-order layers.

Multicast/broadcast channels are used for the broadcasting ofinformation signals.

The aforementioned physical channels of W-CDMA and HSDPA are describedin “Tachikawa Keiji, W-CDMA Mobile Communication Method,ISBN4-621-04894-5” and the like.

FIG. 14 and FIG. 15 are tables describing the relationships between themaximum delay time (n−1)T between transmission antennas and thefrequency bandwidth F_(c) of chunks in connection with physicalchannels. As shown in the figures, it is preferable to set(n−1)T<1/F_(c) irrespective of the frequency diversity region and themultiuser diversity region with respect to common control pilotchannels, common control channels, and dedicated control channels. It ispreferable to set (n−1)T>1/F_(c) irrespective of the frequency diversityregion and the multiuser diversity region with respect to downlinksynchronization channels.

With respect to dedicated pilot channels, it is preferable to set(n−1)T>1/F_(c) in the frequency diversity region and to set(n−1)T<1/F_(c) in the multiuser diversity region. Suppose that dedicatedpilot signals are transmitted via transmission antennas, wherein thedelay imparting section for delaying transmission signals supplied to ntransmission antennas by the maximum delay time (n−1)T or less sets thedelay time T such that the maximum delay time (n−1)T falls within arange of (n−1)T>1/F_(c) when a communication signal, which indicateswhether chunks including dedicated pilot channels are subjected to thefrequency diversity transmission or the multiuser diversitytransmission, indicates frequency diversity, while it sets the delaytime T so as to perform directivity control using weights output fromthe weight calculation section or to define the maximum delay time(n−1)T as (n−1)T<1/F_(c) when the communication signal indicatesmultiuser diversity.

Multicast/broadcast channels are used in the frequency diversity regiononly; hence, it is preferable to set (n−1)T>1/F_(c).

The reasons why the aforementioned setups are performed are that commonpilot channels are used for the notification of signal intensitiesobserved by terminals, hence, it is undesirable that the delay timevaries with respect to chunks, while it is necessary for the wirelesstransmission device to know signal intensities with respect to chunks incase of (n−1)T<1/F_(c) in order to perform multiuser diversity, hence,it is preferable to set (n−1)T<1/F_(c) in order that the maximum delaytime does not vary with respect to chunks.

Dedicated pilot channels are used for calculations of estimated valuesof propagation paths used for demodulation of data signals. Therefore,it is preferable to perform communication by setting (n−1)T>1/F_(c) inthe frequency diversity region and by setting (n−1)T<1/F_(c) in themultiuser diversity region.

Downlink synchronization channels are used for frame synchronization,wherein the estimation of propagation paths is not necessary, and it ispreferable to secure accurate reception in case of low reception power;hence, it is preferable to set (n−1)T>1/F_(c) in order to produce thefrequency diversity effect. In particular, there is a possibility thatthe same signal is transmitted using the same time and the samefrequency via downlink synchronization channels by way of plural sectorsand plural antennas included in a single base station. Therefore,signals are applied with different delays with respect to antennas andare transmitted by way of plural sectors and plural antennas included ina single base station via downlink synchronization channels; thus, it isexpected to produce a high frequency diversity effect, which is higherthan that of another physical channel.

It is presumed that common control channels and dedicated controlchannels use estimated values of propagation paths, which are producedby way of common pilot channels; hence, it is preferable that they beset to the maximum delay time, which is identical to that of the commonpilot channels, and be subjected to transmission.

However, it is preferable to secure accurate reception in common controlchannels and dedicated control channels in case of low reception power;hence, it is preferable to produce the frequency diversity effect,wherein, in consideration of improvement of reception performance ofcontrol channels at first, when common control channels, dedicatedcontrol channels, and multicast/broadcast channels are included in thesame chunk, it is preferable to perform transmission via common pilotchannels by setting (n−1)T>1/F_(c), thus producing the frequencydiversity effect in control channels.

When the same chunk is used for the multiuser diversity, it is necessaryto perform notification about signal intensities emerging in actualtransmission suited to the multiuser diversity (communication under(n−1)T<1/F_(c)); hence, it is preferable to perform transmission bysetting (n−1)T<1/F_(c).

For this reason, it is possible to set the relationship between themaximum delay time (n−1)T between transmission antennas and thefrequency bandwidth F_(c) of the chunk, which is identical to therelationship shown in FIG. 15, with respect to each physical channel.

In order to produce the frequency diversity effect, it is preferable toperform communication by setting (n−1)T>1/F_(c).

The aforementioned embodiment is described such that the maximum delaytime falls within a range of (n−1)T<1/F_(c) in the multiuser diversityregion, whereas, the wireless transmission device described in the fifthembodiment can use the weight w_(m), which is produced by the weightcalculation section 310, in the multiuser diversity region.

The aforementioned second to fifth embodiments are each described suchthat the wireless transmission device having n transmission antennastransmits signals applied with a prescribed delay time with respect toeach of n transmission antennas; but this constitution is notrestrictive. For example, when the wireless transmission device having ntransmission antennas selects using the multiuser diversity, it ispossible to transmit signals applied with a prescribed delay time T′with respect to each of j transmission antennas (where j is an integer,1≦j<n) within n transmission antennas.

In the aforementioned constitution compared with the constitution inwhich signals are transmitted using all the n transmission antennas, amaximum delay time (j−1)T′ applied to signals transmitted via jtransmission antennas decreases so as to further reduce variations ofpropagation paths; hence, it is possible to produce a good multiuserdiversity effect. In case of j=1, in particular, it is possible toreduce the circuit scale of the delay section.

The present embodiment is described under the precondition that themaximum delay time is set as (n−1)T>1/F_(c) in order to produce thefrequency diversity effect, whereas, as described in the firstembodiment, when transmission is performed using a physical channel,which is assigned with chunks lying in plural frequency directions, thebandwidth BW assigned to the physical channel forms the basis forproducing the frequency diversity effect; hence, it is possible toproduce the frequency diversity effect by setting the maximum delay timeto (n−1)T>1/BW.

By use of the wireless transmission device, according to theaforementioned embodiments of the present invention, which selects theuse of either the frequency diversity or the multiuser diversity intransmission of signals from n transmission antennas so as to vary delaytimes applied to signals transmitted via n transmission antennas on thebasis of the selection result; hence, it is possible to produce thefrequency diversity effect or the multiuser diversity effect withoutbeing affected by conditions of propagation paths.

In the aforementioned embodiments, programs realizing functions of theerror correcting coding section 13, the modulator 14, the sub-carrierassignment sections 15 and 215, the IFFT section 16, the parallel-seriesconversion section 17, the GI imparting section 18, the delay impartingsections 19-1 to 19-3, the circulating delay imparting sections 119-1 to119-3, the mixing section 20, the filter 21, the D/A converter 22, thephase rotation section 219, the weight calculation section 310, and theweighted multiplication section 319 shown in FIGS. 8, 10, 12, and 13 arestored in computer-readable storage media, so that the programs storedin the storage media are loaded into a computer system and are thenexecuted so as to control the wireless transmission device. Herein, thecomputer system includes OS and the hardware such as peripheral devices.

The computer-readable recording media are referred to as flexible disks,magneto-optical disks, ROM, portable media such as CD-ROM, and storagedevices such as hard disks incorporated in the computer system.Furthermore, the computer-readable storage media embrace media fordynamically retaining programs in a short period of time, such ascommunication lines such as the Internet, networks, and telephone linesused for transmitting programs as well as volatile memories forretaining programs for a prescribed period of time, which areincorporated in the computer system serving as the server and client.The aforementioned programs are designed to realize a part of theaforementioned functions; alternatively, they are designed to realizethe aforementioned functions by way of the combination with programsthat are stored in the computer system in advance.

This invention is described in detail by way of the embodiments withreference to the drawings, wherein the detailed constitution thereof isnot necessarily limited to the embodiments; hence, it embraces designsthat do not deviate from the spirit of this invention.

INDUSTRIAL APPLICABILITY

The present invention is applicable to wireless transmission devices andwireless transmission methods, which transmit signals to wirelessreception devices by use of plural transmission antennas, wherein delaytimes are appropriately set based on the determination as to whethertransmission signals are subjected to frequency diversity transmissionor multiuser diversity transmission; hence, it is possible to producefrequency diversity effects and multiuser diversity effects withoutbeing affected by conditions of propagation paths.

1. A transmission control method adapted to a transmission apparatus ina transmission system in which slots are assigned to chunks divided in afrequency domain and in a time domain, said transmission control methodcomprising: imparting delays to signals being supplied to a plurality oftransmission antennas; controlling the delays, at a first instance, suchthat a maximum delay time among the plurality of transmission antennasis set to a third value larger than 1/Fc where Fc denotes a frequencyband width of each chunk with respect to a multicast/broadcast channel;and controlling the delays, at a second instance, such that a maximumdelay time among the plurality of transmission antennas is selectivelyset to either a first value smaller than 1/Fc or a second value largerthan 1/Fc with respect to another physical channel, wherein thecontrolling of the delays is performed in the transmission apparatus. 2.The transmission control method according to claim 1, wherein a delaytime T is set to a second transmission antenna on the basis of a firsttransmission antenna, and wherein delay times are sequentially increasedwith respect to a third transmission antenna and its subsequenttransmission antenna on the basis of the first transmission antenna by amultiple of the delay time T.
 3. The transmission control methodaccording to claim 1, wherein the delays imparted to the signals beingsupplied to the plurality of transmission antennas are controlled. 4.The transmission control method according to claim 1, wherein themaximum delay time is reduced by decreasing the number of thetransmission antennas used for transmitting the signals.
 5. Thetransmission control method according to claim 1, wherein the maximumdelay time is controlled by imparting the delays in the time domain. 6.The transmission control method according to claim 5, wherein the delaysare imparted to the signals being supplied to the transmission antennasin units of valid symbols so that a guard interval is applied to eachunit of the guard symbol having the delays, thus controlling the maximumdelay time.
 7. The transmission control method according to claim 1,wherein the maximum delay time is controlled by imparting the delays inthe frequency domain.
 8. The transmission control method according toclaim 7, wherein the transmission system is a multicarrier transmissionsystem, and wherein the signals which are processed in units of usersare allocated to subcarriers so that a predetermined amount of phaserotation is performed in units of subcarriers, thus controlling themaximum delay time.
 9. The transmission control method according toclaim 1, wherein the third value is the same value as the second value.10. The transmission control method according to claim 1, wherein thethird value is a different value than the second value.